Diabetes mellitus is characterized in two broad groups based on clinical manifestations, namely, the non-insulin-dependent or maturity onset form, also known as Type 2; and the insulin-dependent or juvenile onset form, also known as Type 1. Clinically, the majority of Type 2, maturity onset diabetics are obese, with manifestations of clinical symptoms of the disease usually appearing at an age over 40. In contrast, Type 1, juvenile onset patients are not over-weight relative to their age and height, with rapid onset of the disease at an early age, often before 30, although Type 1 diabetes can occur at any age.
Diabetes mellitus is a metabolic disorder in humans with a prevalence of approximately one percent in the general population, with one-fourth of these being the Type 1, insulin-dependant category (Foster, D. W., Harrison's Principles of Internal Medicine, Chap. 114, pp. 661-678, 10th Ed., McGraw-Hill, New York). The disease manifests itself as a series of hormone-induced metabolic abnormalities which eventually lead to serious, long-term and debilitating complications involving several organ systems including the eyes, kidneys, nerves, and blood vessels. Pathologically, the disease is characterized by lesions of the basement membranes, demonstrable under electron microscopy.
Type 1 diabetics characteristically show very low or immeasurable plasma insulin with elevated glucagon. Regardless of what the exact etiology is, most Type 1 patients have circulating antibodies directed against their own pancreatic cells including antibodies to insulin, to islet of Langerhans cell cytoplasm and to the enzyme glutamic acid decarboxylase. An immune response specifically directed against beta cells (insulin producing cells) leads to Type 1 diabetes. This specificity is supported by the above clinical picture, since beta cells secrete insulin while alpha cells secrete glucagon.
Current therapeutic regimens for Type 1 diabetes include modifications to the diet in order to minimize hyperglycemia resulting from the lack of natural insulin, which in turn, is the result of damaged beta cells. Diet is also modified with regard to insulin administration to counter the hypoglycemic effects of the hormone. Whatever the form of treatment, parenteral administration of insulin is required for all Type 1 diabetics, hence the term "insulin-dependent" diabetes.
Conventional insulin therapy is limited to the parenteral (i.e. subcutaneous) administration of insulin. Oral administration of insulin has not been possible because the insulin molecule cannot pass through the digestive tract in a sufficiently intact form to provide its therapeutic benefit. There has been an ongoing search by those skilled in the art for an alternative method to eliminate or reduce the need for insulin because of the numerous problems associated with subcutaneous administration of the drug. Among the methods that have been investigated are implantable insulin pumps and pancreatic islet cell transplantation.
Because Type 1 diabetes usually manifests itself in adolescents and because the subcutaneous delivery of insulin requires strict, self-regimentation, compliance is often a serious problem. In addition, the act of the parenteral administration itself can be very traumatic to juveniles. For the clinician, it is difficult to precisely regulate the amounts of insulin needed at any given time of the patient's day. Furthermore, it is all but impossible to regulate blood glucose levels in diabetic patients with parenteral insulin to the extent to which blood glucose is regulated in normal individuals.
Thus, in the early stages of treatment of Type 1 diabetes, patients often become either hyperglycemia or hypoglycemic because the exact timing of the insulin injections and levels of insulin needed are not known. As treatment progresses the clinician and, more importantly, the patient adjusts to the daily routine, but there is always the risk of ketoacidosis or hypoglycemia.
In addition, some patients produce antibodies to the injected insulin even though most patients are now treated with human insulin produced by recombinant technology. This can lead to the need for higher doses of insulin. To date, there has been no successful oral dosage form containing insulin.
The art has long sought a method for preventing and/or treating Type 1 diabetes which does not involve parenteral administration of insulin. Various attempts at alternate delivery methods for insulin have failed or have not progressed to a practical level. For example, oral insulin, transcutaneous insulin delivery, and nasal insulin have not become clinically utilized. Oral insulin does not affect blood glucose levels. Because it has been necessary to inject lipids into mammals receiving nasal insulin in order to get the insulin across the nasal mucosa, this route of insulin administration has been limited.
Oral dosage forms for treatment of Type 2 diabetes are available, (e.g. oral sulfonylureas). These orally administered agents do not comprise insulin but rather stimulate the pancreas to produce insulin, and are only effective for treatment of certain forms of Type 2 diabetes. As for Type 1 diabetes, oral agents such as sulfonylureas are ineffective due to markedly diminished or damaged beta-cell mass (Foster, D. W., Harrison's Principles of Internal Medicine, Chap. 114, p. 668, 10th Ed., McGraw-Hill, New York).
Type 1 diabetes is considered to be a disease of autoimmune etiology (Eisenbarth, G. S., New Engl. J. Med. 314: 1360-1368, 1986). Various animal models are available for the study of Type 1 diabetes as an autoimmune disorder. These include the BB mouse (Nakbookda, A. F., et al., Diabetologic 14: 199-207, 1978) and the NOD (non-obese diabetic) mouse in which diabetes develops spontaneously (Prochazka et al. Science 237:286, 1987). Islet-cell specific, CD4 and CD8 T-lymphocytes have been implicated as causative agents for damage to beta cells, demonstrated by decreased incidence of Type 1 diabetes in NOD mice (J. Exp. Med. 166:823, 1987).
Other therapies are being developed for the treatment of autoimmune diseases in general.
Weiner et al., U.S. patent application Ser. No. 460,852 filed Feb. 21, 1990, now abandoned (the national stage of PCT Application No. PCT/US88/02139, filed Jun. 24, 1988), which is a continuation-in-part application of U.S. patent application Ser. No. 065,734 filed Jun. 24, 1987, now abandoned discloses the treatment of autoimmune diseases by oral administration of autoantigens.
Weiner et al., U.S. patent application Ser. No. 454,806 filed Dec. 20, 1989, now abandoned discloses the aerosol administration of autoantigens, disease-suppressive fragments of said autoantigens and analogs thereof as an effective method for treating T-cell mediated autoimmune diseases.
Weiner et al., U.S. patent application Ser. No. 487,732, filed Mar. 2, 1990, now abandoned discloses synergists (enhancers) for use with oral administration of autoantigens, disease suppressive fragments and analogs thereof as effective treatments for T-cell mediated autoimmune diseases.
Weiner et al., U.S. patent application Ser. No. 551,632 filed Jul. 10, 1990, now abandoned as a Rule 62 continuation-in-part application of U.S. patent application Serial No. 379,778, filed Jul. 14, 1989 (now abandoned), discloses methods of preventing or treating uveoretinitis in mammals by oral administration of purified S antigen.
Nagler-Anderson, et al., (Proc. Natl. Acad. Sci (USA) 83: 7443-7446, 1986), describe the oral administration of collagen to suppress collagen-induced arthritis in a mouse model.
However, none of the above-mentioned for treatments for autoimmune diseases can be used treating Type 1 diabetes because the antigens involved in eliciting and maintaining the Type 1 disease have not been identified.
It is, therefore, an object of the present invention to provide agents and methods for treating and preventing autoimmune diseases in mammals having the characteristics of Type 1 diabetes. Prevention of Type 1 diabetes preferably involves treatment to hyperglycemia.
Another object of the present invention is to provide compositions and pharmaceutical formulations useful for treating mammals suffering from autoimmune diseases having the characteristic of Type 1 diabetes.
A still further object of the invention is to provide compositions and pharmaceutical formulations useful for oral administration to mammals for the purpose of preventing or attenuating the manifestations (i.e. clinical symptoms) of autoimmune diseases having the characteristics of Type 1 diabetes. Prevention of Type 1 diabetes includes treatment prior to hyperglycemia.
These and other objects of the present invention will be apparent to those of ordinary skill in the art in light of the following.